The present invention generally relates to furnaces, and more particularly to improved two-stage furnaces with two stage thermostats.
Air comfort control devices are used to set the temperature of an at least partially enclosed environment such as a room, a house, a motor home, etc. Regulation of the operation of air comfort control devices such as furnaces and air conditioners can be accomplished through various electronic controllers. Such controllers can set a furnace such as a gas burning furnace to a high BTU setting or a low BTU setting. The high BTU setting is used to rapidly heat the partially enclosed environment when the temperature is substantially below a desired temperature. When the temperature approaches the desired temperature (generally within a few degrees Fahrenheit) the furnace switches to the low BTU setting to provide a more gradual rise and reduce overshoot of the desired temperature. Such two stage furnaces may be controlled by two stage thermostat controllers and also allow manual control of the furnace to either BTU setting.
When heating is not necessary it may still be desirable to circulate air throughout the partially enclosed environment through the use of a fan. Some air comfort control devices have separate fans for cooling and for heating. This is especially true of air comfort control devices used in recreational vehicles and motor homes where a separate furnace and air conditioner are typically used. It would be desirable to have a temperature controller which controlled both the furnace fan and the air conditioner fan so that they could operate simultaneously.
Gas furnaces typically have a gas valve connected to a gas source, an igniter and a blower motor. The blower motor rotates the furnace fan. In known furnaces, particularly residential furnaces which rely on common 110 V AC power sources, an ignition controller which also controls the motor sends a constant voltage to different portions of windings of a multi-speed blower motor to affect different furnace fan speeds. In some applications, especially recreational vehicles, a 100 V AC power supply may not be readily available. It would be desirable to have a controller which can account for irregular power supplies to provide current to a blower motor and generate multiple furnace fan speeds.
Known furnace controllers typically have one controller which controls both the blower motor and the gas valve (in response to input signals from the thermostat) and also performs all of the mandated safety checks, including, for example, checking sail switches and limit switches and other diagnostics. It would be desirable to be able to replace components directed to safety and diagnostic control independent of components directed to control of the blower motor and the gas valve.
In view of the foregoing, it is an object of the present invention to provide an air comfort control device capable of controlling an air conditioning fan and a furnace fan. It is an additional object of the present invention to provide an air comfort control device where a motor controller which can supply current to a single speed blower motor and generate multiple furnace fan speeds. It is an additional object of the present invention to provide a furnace with a separate motor controller and ignition controller. It is still another object of the present invention to incorporate microprocessor controls into the air comfort control device to provide greater control of furnace operation and increase customer setting options. It is still another object of preferred embodiments of the present invention to provide an air comfort control device that is of low cost, compact size, easy to manufacture and which is highly reliable in operation.
In accordance with a first aspect, there is provided an air comfort control device comprising a furnace having a furnace fan, an air conditioner having an air conditioner fan positioned remote from the furnace fan, and a temperature controller responsive to temperature changes in air in a partially enclosed environment and adapted to receive a fan input signal. The temperature controller sends a fan output signal to both the furnace fan and the air conditioner fan to run together to circulate air through the partially enclosed environment. Preferably wherein the temperature controller is adapted to receive several different input signals, including a temperature input signal, a desired temperature input signal, and a mode input signal. Based on these input signals the thermostat controller sends output signals to the furnace, advantageously permitting an operator to choose one of many different settings for enhanced comfort.
In accordance with another aspect, a comfort control device has a blower motor that rotates the furnace fan at either a high speed or a low speed, and a motor controller which in response to a fan output signal from the temperature controller sends a first voltage to actuate the blower motor so that the furnace fan rotates at the high speed and a second voltage different from the first voltage to actuate the blower motor so that the furnace fan rotates at the low speed.
In accordance with another aspect, a comfort control device further comprises a gas valve having a closed position and an open position, and when the gas valve is in the open position it is further in one of a high position and a low position. An ignition controller sends a signal to the move the gas valve between the open and closed positions. The motor controller is separate from the ignition controller. In response to a signal from the temperature controller the motor controller sends a motor control signal to actuate the blower motor so that the furnace fan rotates at one of the high speed and the low speed and sends a secondary valve signal to move the gas valve to one of a high position and a low position.
From the foregoing disclosure and the following more detailed description of various preferred embodiments it will be apparent to those skilled in the art that the present invention provides a significant advance in the technology and art of furnaces, particularly two-stage furnaces. Particularly significant in this regard is the potential the invention affords for providing a furnace that is reliable, durable and has a long life. Additional features and advantages of various preferred embodiments will be better understood in view of the detailed description provided below.